June 24, 2009--Mysterious "blobs" of glowing gas in far-flung regions of space are mysteries no more, according to astronomers using NASA's Chandra X-ray Observatory.

The huge reservoirs of hydrogen gas were found about a decade ago during surveys of young, distant galaxies. The blobs glow brightly in visible light, but the sources of immense energy required to power the glow remained unclear.

Now, in new images from Chandra, scientists have found evidence that the gas blobs are being heated by the growth of nearby galaxies with supermassive black holes at their hearts. Above, a still from an animation shows how the black hole in a spiral galaxy, like our Milky Way, might send out pulses of heat that illuminate the surrounding gas.

Galaxies grow as interstellar gases drawn in by gravity cool and condense to form new stars. But eventually a buildup of heat in the surrounding gas triggers the galaxies to slow down their growth, scientists say.

"We're seeing signs that the galaxies and black holes inside these blobs are coming of age and are pushing back on the gas [being pulled in by gravity] to prevent further growth," study co-author Bret Lehmer, of Durham University in the U.K., said in a statement. "Massive galaxies must go through a stage like this or they would form too many stars and so end up ridiculously large by the present day."